Syrian rebels are accusing government forces of moving chemical weapons close to the country's borders.

Brigadier Kassem Saeddine of the opposition Free Syrian Army said the rebels have "confirmed information that the weapons were moved to airports located at the borders of Syria."

No confirmation of the claim was available from the government or other sources.

The rebel claim on July 24 came one day after a Syrian Foreign Ministry spokesman, Jihad Makdissi, warned that the government could use chemical weapons if Syria is attacked by an external force.

The statement marked the first time that Syria's government has acknowledged it possesses chemical weapons.

In his statement, the Syrian spokesman said the government would only use chemical weapons in response to "aggression" coming from outside the country.

He said authorities would never use such weapons against Syrians.

"Any stocks of [weapons of mass destruction] or any unconventional weapons that the Syrian Arab Republic possesses would never...be used against civilians or against the Syrian people during this crisis [under] any circumstances, no matter how the crisis would evolve," Makdissi said.

He added that the country's chemical-weapons stockpiles remain well-protected by the military, despite the conflict engulfing the nation since March 2011.

Russia, a longtime Syria ally, criticized Damascus over its threat. The Russian Foreign Ministry in a statement reminded Syria that it had ratified a global convention banning the use of chemical weapons and said that Russia expects Syria to "unfailingly honor its international obligations."

Obama Warning

Reacting to this statement, U.S. President Barack Obama warned on July 23 that Syrian President Bashar al-Assad and his regime would be held responsible by the international community if it used chemical weapons.

"Today we're also working so that the Syrian people can have a better future, free of the Assad regime," he said. "Given the regime's stockpiles of chemical weapons, we will continue to make it clear to Assad and those around him that the world is watching and that they will be held accountable by the international community and the United States should they make the tragic mistake of using those weapons."

Amos Gilad, a defense official of Syrian neighbor and rival Israel, said on July 24 that Israel's government believes the Syrian regime still has full control of its chemical weapons.

He told Israeli radio: "At the moment, the entire nonconventional weapons system is under the full control of the regime."

Syria has neither signed nor acceded to the global Chemical Weapons Convention aimed at restricting such arms.

Damascus has officially stated that while it supports a Middle East-wide ban on weapons of mass destruction, it cannot unilaterally renounce chemical arms as long as Israel continues to pose a threat to its security.

Analysts say that since 1973, Syria appears to have acquired the ability to develop and produce chemical-weapons agents, including mustard gas and sarin, and possibly also the VX nerve agent, which is classified as a dangerous weapon of mass destruction by the United Nations.

The exact amounts of such weapons in the Syrian stockpile are not known.

However, the U.S. Central Intelligence Agency has estimated that Syria possesses several hundred liters of chemical weapons and produces hundreds of tons of agents annually.

Ali Mamlouk, head of Syria's Internal Security Directorate, was appointed head of national security.

Abdul-Fattah Qudsiya, head of military intelligence, was named Mamlouk's deputy.

The new appointees are known regime figures and close associates of the president, making it unlikely that the reshuffle will alter the government's efforts to defeat anti-Assad rebels.

Meanwhile, U.S. Secretary of State Hillary Clinton says the rebels are making territorial gains that will eventually become "safe havens" and provide a base for further operations against government forces.

She also told reporters in Washington that despite the opposition gains, it was not too late for Assad to begin planning for a political transition to end the violence.